1. Children or adults (regardless of age) without a known or fully defined immunodeficiency and with a definitively diagnosed severe viral infection, including infection caused by herpesviruses (HSV-1, HSV-2, CMV, EBV, VZV, HHV-6, HHV-7, HHV-8), human papillomavirus (e.g., severe recalcitrant warts), adenovirus, polyomavirus (such as JC virus and BK virus), or influenza virus. Viral infections that would be considered "opportunistic-like", such as herpesvirus esophagitis, herpesvirus encephalitis, CMV colitis, or progressive multifocal leukoencephalopathy (caused by the JC polyoma virus), will be of particular interest in this protocol.